1. Field of the Invention
The invention relates to a vehicle control system, and more particularly to a vehicle control system for a vehicle that uses an electric oil pump to cool a rotating electrical machine.
2. Description of Related Art
A vehicle installed with a rotating electrical machine uses an oil pump that circulates a coolant in order to cool the rotating electrical machine. A vehicle installed with both a rotating electrical machine and an engine uses a mechanical oil pump connected to an output rotary shaft of the engine. When the engine stops, the mechanical oil pump also stops operating. Therefore, while the engine is stopped, an electric oil pump that is driven independently of an operation of the engine is used to cool the rotating electrical machine.
Japanese Patent Application Publication No. 2004-256063 (JP 2004-256063 A), for example, describes a control apparatus for a vehicle in which an oil pump driven by a motor/generator (M/G) or an electric oil pump is driven when, during execution of a fuel cut, a deficiency occurs in a discharge amount of a mechanical oil pump driven by an engine.
The electric oil pump can be driven independently of the engine and so on, but when air or the like is intermixed in the circulating coolant, idling occurs in the electric oil pump such that the coolant cannot be circulated sufficiently.